Radiative transfer simulation for the optical and near-infrared electromagnetic counterparts to GW170817

TL;DR

This paper presents a 2D radiative transfer simulation of kilonova lightcurves from GW170817, successfully reproducing observed features by considering multiple ejecta components simultaneously.

Contribution

It introduces a novel 2D radiative transfer model that accounts for the interaction of different ejecta components in kilonova simulations.

Findings

Lightcurves and velocities match observations with realistic ejecta parameters.

The model resolves previous discrepancies in ejecta mass and velocity assumptions.

Simulations align with numerical-relativity predictions.

Abstract

Recent detection of gravitational waves from a binary-neutron star merger (GW170817) and the subsequent observations of electromagnetic counterparts provide a great opportunity to study the physics of compact binary mergers. The optical and near-infrared counterparts to GW170817 (SSS17a, also known as AT 2017gfo or DLT17ck) are found to be consistent with a kilonova/macronova scenario with red and blue components. However, in most of previous studies in which contribution from each ejecta component to the lightcurves is separately calculated and composited, the red component is too massive as dynamical ejecta and the blue component is too fast as post-merger ejecta. In this letter, we perform a 2-dimensional radiative transfer simulation for a kilonova/macronova consistently taking the interplay of multiple ejecta components into account. We show that the lightcurves and photospheric velocity of SSS17a can be reproduced naturally by a setup consistent with the prediction of the numerical-relativity simulations.